Force received from wind 1 (Effect of size)

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What type of experiment is this?

Experimental procedure and explanation:

• What happens to the force received from the wind that acts on a thing when we change the size of the thing?
• Let us compare the effect of the wind force using one and two square bars. We examine the magnitude of the force caused by the wind based on the elongation of the rubber string when exposed to the wind.
• With one bar, the rubber stretches to about 32 cm. When there are two bars, it extends up to about 60 cm. The bigger the thing, the greater is the force attributed to the wind (air resistance).
• In the case of two bars, the area from the front is twice that of one bar. The force attributed to the wind is doubled. The force attributed to the wind will be doubled if the area is doubled for the same shape.

[Development]	Drag FD (such as air resistance, water resistance) can be expressed by the formula (Drag FD) ＝ (Drag coefficient CD) × (Fluid density ρ) × (Speed U)2 × (Frontal projected area S) ÷ ２ Here, the drag coefficient CDis determined by the shape of the object; the frontal projected area S represents the area of the figure when the object is viewed from the front. This equation indicates that the drag FDis almost proportional to S (it becomes “almost proportional” because CDmay change).
[Keywords]	Air resistance, Drag
[Related items]	Function of wind and rubber, Large Ball and Small Ball
[Reference]	“The Wonders of Flow”, Japan Society of Mechanical Engineering, Kodansha Blue Backs, P148-155. “Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natsume Publishing, P54-55, P58-63, and P74-75.

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